1. Field of the Invention
The present invention relates to an improvement in the drilling of highly angulated wellbores with a rotary rig which has a drill string terminated with a bit and which employs circulating drilling mud.
2. Description of the Prior Art
As those skilled in the art are aware, the art of drilling wellbores is highly developed, and a number of devices and developments which are useful in drilling vertical wellbores with a rotary rig having recirculating mud are available. Also, horizontal augers are employed for drilling relatively short horizontal bores.
With depleting oil reserves, a need exists for improved efficiencies in drilling wellbores and recovering oil from the remaining reserves. One means of increasing efficiency is by use of highly angulated wellbores, which in many cases are horizontal or nearly horizontal. Such wellbores are often drilled with conventional rotary rigs having a drill string terminated with a bit wherein drilling mud is pumped down the drill string to exit at or near the drill bit so as to remove cuttings from the wellbore, cool the bit, and provide pressure control. When horizontal or highly angulated wells are drilled, particularly over a substantial horizontal distance, a problem of removing the cuttings from the horizontal or highly deviated wellbore arises because the cuttings settle out of the mud onto the bottom of the angulated hole.
Another problem that arises is that wear on the drill string is often substantially increased.
Particularly when long outreach highly angulated or horizontal wells are drilled, the drill string also becomes subject to substantially increased torsional stresses and stresses leading to buckling.
Some devices and developments known to be useful for drilling vertical wellbores with a rotary rig or with horizontal augers for drilling relatively short horizontal bores have a superficial relationship to the invention of this application. The prior art statement which is filed concurrently with this patent application notes references to such devices and developments and comments on their relationship to the invention at hand. In general, the prior art developments relate to different systems than drilling highly angulated wells with a rotary rig having a drill string terminated with a bit which employs circulating drilling mud, and such developments function in a different manner such as to obtain different results than is the case with the invention disclosed and claimed herein.
The invention of the application addresses the need for improved equipment and methods for drilling the highly angulated wellbores which are useful to more efficiently recover remaining oil reserves. It fulfills a need of the industry to solve problems associated therewith such as are noted above.